The present invention relates to devices that dispense air treatment chemicals from a substrate using the heat of a candle to drive the dispensing. More particularly, the invention relates to such devices that have been configured to protect the air treatment chemical from heat degradation (a/k/a “pyrolysis”) during such dispensing.
A variety of devices are known for dispensing volatilizable air treatment chemicals such as pest control materials (e.g., insecticides, insect repellents, or insect growth control regulators), air scents or deodorizers (e.g. masks), allergen control ingredients, disinfectants, sanitizers or other materials. In some of these devices the air treatment chemical is mixed with candle wax and is dispensed during a candle burning process (where the chemical is released primarily from the heated wax surrounding the wick). While this is a common technique for dispensing a variety of fragrances, typically it has been less successful when dispensing certain particularly desirable pest control materials.
Attempts have been made to use the heat from a candle (or other similar heat source) to distribute air treatment chemicals from an adjacent impregnated pad surface or the like. See e.g. U.S. Pat. Nos. 2,742,342, 4,781,895, 6,482,365, 6,503,459, and 7,138,130. However, these devices typically placed the pad directly over the candle flame, leading to heat spikes directly ever the flame, as wed as sometimes too little heat adjacent the periphery of the pad.
Another approach was to position a chimney directly over the candle flame, with the impregnated substrate positioned around the chimney. See e.g., U.S. Pat. No. 8,047,837. While this made the pad able to more efficiently dispense some additional types of air treatment chemicals, it did not completely address pyrolysis and/or uneven healing problems.
Still another approach was disclosed in U.S. patent application publication 2009/0004067. There, an air treatment chemical was coated on a radially outer periphery of a candle cap. The heat of the candle heated the walls of the candle cup, and that heat was used to drive the air treatment chemical off. However, this type of heat transfer was relatively inefficient, and (in any event) placing the active at a typical gripping position for the candle could cause some consumers to have concerns about the possibility of touching and/or interfering with the active.
Thus, a need continues to exist for improved candle dispensers where the heat of a candle drives an air treatment chemical off of a carrier substrate, albeit with reduced pyrolysis concerns.